MADRID (AP) A doctor treating Diego Costa for a hamstring injury said the striker has a muscle tear that needs to be reassessed in 15 days, raising doubts about his chances of making Spain's World Cup squad.

Pedro Guillen of the Cemtro clinic told the Cadena Cope radio station on Tuesday that the 25-year-old Brazil-born player had a "grade one tear to the femoral biceps of his right leg," and would need 15 days convalescence before his injury could be re-evaluated.

"Costa is still carrying the injury, a micro-tear," said Guillen, who examined the forward.

Spain's opener in Brazil is June 13 against the Netherlands. The injury rules Costa out of Spain's pre-World Cup friendly matches against Bolivia and El Salvador.

Coach Vicente del Bosque said Sunday the players in his 23-man squad would need to be fit by June 2 - the FIFA deadline for squad lists.

Speaking at the Spain squad training ground Tuesday, striker Fernando Torres said muscle injuries like Costa's were tricky because they can take weeks to heal.

"Costa has to see if he is fit," said Torres, adding that the medical team would also have to assess the rate of his recovery to see "if he can make it in optimum condition."

Torres said the fact that Del Bosque was prepared to wait for Costa showed his importance within the squad.

The 30-year-old Chelsea and Spain striker said Group B was "a tough one for both Holland and Spain," and that the match against the Dutch would be good because "they will be out for revenge" - a reference to Spain's victory over the Netherlands in the last World Cup final.

Costa committed himself to play for Spain - instead of Brazil - last year and played his first match with the world and European champions in March.

He has scored 36 goals in all competitions and helped Atletico Madrid secure its first La Liga championship in 18 years and reach the Champions League final, which his team lost 4-1 to Real Madrid after extra time.